The invention relates to a hydraulic cam follower, especially for a tappet pushrod valve train of an internal combustion engine, which is provided for installation at an angle to the direction of the force of gravity, with a pot-shaped housing, whose bottom is provided with at least one cam contacting element, wherein in the housing there are two guides, in each of which a pressure piston is arranged so that it can move in the axial direction, wherein each end of the pistons is provided as an installation for contact with a respective tappet pushrod.
Such cam followers for the simultaneous actuation of several identically operating gas-exchange valves (preferably two, but not a requirement) do not have to be explained in more detail at this point. Their installation at an angle to the direction of the force of gravity comes into question, in particular, when they are used in V-type engines with a camshaft being located underneath.
In general, the goal of greater reduction in the oscillating valve train masses leads to the increase in the miniaturization of such cam followers. In this way, the amount of hydraulic medium that can accumulate in the reservoir of the pressure piston of the cam follower necessarily decreases. In other words, the ratio of reservoir volume to high-pressure space volume becomes less favorable. If such cam followers are installed, as above, at an angle to the direction of the force of gravity, then under unfavorable circumstances, the otherwise only small amount of hydraulic medium in the reservoir can run out successively after the internal combustion engine is stopped or, in general, this amount of hydraulic medium can be insufficient for non-knocking engine operation, especially when the internal combustion engine is started up again (after a long time standing still). Exactly those pressure pistons standing at the valve lift when the internal combustion engine is stopped are here at the most danger.
In the state of the art (see DE 10 2004 019 282 A1), for tappet pushrod valve trains with so-called “top-down oiling” it was attempted to use the tappet pushrod as a reservoir for hydraulic medium. Such a measure is rather complicated in terms of construction effort and cannot be applied to a plurality of valve trains with oil supply systems that deviate from the above.